Processes of determining characteristics of a surface of a papermaking fabric

ABSTRACT

Processes of determining features of a paper-making fabric. The processes utilize a representation of a portion of a surface of the fabric, with the representation showing at least one of (i) locations and (ii) sizes of knuckles and pockets in the surface of the fabric. An image of the portion of the fabric is generated based on the representation. Using the displayed image, an outline is drawn around at least one of the knuckles, and guidelines are drawn such that the guidelines at least one of (i) pass through the center of the outlined knuckle, (ii) pass through the other knuckles, and (iii) form a shape that surrounds areas of the image that correspond to where the pockets are formed between the knuckles. With the outlined knuckle and guidelines, properties that affect the paper-making functionality of the fabric may be calculated.

CLAIM OF PRIORITY

This application is a continuation of copending U.S. patent applicationSer. No. 15/164,932, filed May 26, 2016, which is a continuation of U.S.patent application Ser. No. 14/283,530, filed May 21, 2014, now U.S.Pat. No. 9,382,663, issued Jul. 5, 2016, which is a continuation-in-partapplication of U.S. patent application Ser. No. 14/077,808, filed Nov.12, 2013, now U.S. Pat. No. 9,349,175, issued May 24, 2016, whichapplication claims the benefit of U.S. Provisional Patent ApplicationNo. 61/725,749, filed Nov. 13, 2012.

FIELD OF THE INVENTION

My invention relates to characterizing the surface of a papermakingfabric. In specific examples, my invention relates to apparatuses,processes, and systems for determining the characteristics of thecontact surface of a fabric that is used for three-dimensionalstructuring of a web in a papermaking process.

RELATED ART

In processes of forming paper products, such as tissue paper and papertowels, three-dimensional shaping is conducted while the papermaking webis still highly deformable, i.e., when the papermaking web has a highwater content. Often, this three-dimensional shaping of the web isconducted on a woven structuring fabric. The fabric provides a contactsurface made up of knuckles in the yarns of the fabric, with pocketsbeing formed in the fabric between the knuckles. When the papermakingweb is applied to the fabric, portions of the web contact the knuckles,and other portions of the web are drawn into the pockets. Before beingremoved from the fabric, the web is dried to a point such that its shapeis fixed or locked. Domes are thereby formed in the dried web where theweb was drawn into the pockets in the fabric, and the domes are presentin the finished paper product. Hence, the paper product has a distinctthree-dimensional structure formed, in part, by the knuckle and pocketcharacteristics of the structuring fabric.

Because the contact surface of a structuring fabric directly relates tothe shape of the finished product, the choice of a structuring fabric isoften based on the shape of the product that is desired. It isdifficult, however, to characterize the contact surface of a structuringfabric based on a simple visual inspection of the fabric. While theknuckles of the fabric can easily be seen, it is often difficult toaccurately determine the sizes of the knuckles, difficult to determinethe areas of the pockets between the knuckles, and difficult todetermine the depth of the pockets into which the papermaking web isdrawn during the papermaking process. As such, there have been previoustechniques that attempt to quantify the characteristics of the contactsurface of the fabric, for example, using formulas based on the yarnparameters of the fabric. It has been found, however, that such formulasare often not accurate enough to characterize the contact surface of thefabric in a manner that allows for an accurate prediction of the paperproduct structure that will be formed with the fabric. Additionally, thecontact area characteristics will often change as the fabric is run on apapermaking machine. For example, wear on the surface of the fabric willgenerally increase the lengths of the knuckles, thereby changing thestructuring that will be imparted on the web by the fabric. Thus,formulas for determining the contact surface characteristics that areapplicable to initial fabric configurations will not necessarily applyto fabrics that have become worn over time.

It would be beneficial, therefore, to provide a technique for accuratelycharacterizing the contact area characteristics of a structuring fabricthat is used in a papermaking process. Moreover, it would be beneficialto provide a technique that can easily determine the contact areacharacteristics as the fabric becomes worn, over time, while the fabricis mounted on a papermaking machine.

SUMMARY OF THE INVENTION

According to a first aspect, my invention provides a process ofdetermining features of a fabric. The process includes forming arepresentation of a portion of a surface of the fabric, therepresentation showing locations and sizes of knuckles and pockets inthe surface of the fabric, generating an image of the portion of thesurface of the fabric based on the representation, displaying at least aportion of the image on a screen associated with a computer having aprocessor, and drawing an outline around at least one of the knucklesdisplayed image. The process further includes drawing guidelines in thedisplayed image such that the guidelines (i) pass through the center ofthe outlined knuckle, (ii) pass through the other knuckles, (iii) form ashape that surrounds areas of the image that correspond to where thepockets are formed between the knuckles. The outline and guidelines aredrawn using an image analysis program stored in a non-transitorycomputer-readable medium.

According to a second aspect, my invention provides a process ofdetermining features of a fabric. The process includes forming arepresentation of a portion of a surface of the fabric, with therepresentation showing locations and sizes of knuckles and pockets inthe surface of the fabric, and the representation being one of a printof the fabric surface and a photograph of the surface of the fabric. Theprocess further includes generating an image of the portion of thesurface of the fabric based on the representation, displaying at least aportion of the image on a screen associated with a computer having aprocessor, determining the sizes and locations of the knuckles in thedisplay of the representation, and determining the sizes and locationsof the pockets in the display of the representation. The process alsoincludes drawing a unit cell for the portion of the surface of thefabric in the displayed image, wherein the unit cell is defined byguidelines that (i) pass through the centers of the knuckles and (ii)form shapes that surround areas of the image that correspond to wherethe pockets are formed between the knuckles. At least one property ofthe surface of the fabric is calculated based on properties of the unitcell formed by the guidelines, and the outline and guidelines are drawnusing an image analysis program stored in a non-transitorycomputer-readable medium.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a paper machine that uses a structuringfabric.

FIG. 2 is a top view of a section of a structuring fabric.

FIGS. 3A and 3B are views of contact surface printing apparatusaccording to the invention.

FIG. 4 is a detailed view of the pressing section of the print formingapparatus shown in FIGS. 3A and 3B.

FIGS. 5A through 5D are examples of prints of structuring fabric madeaccording to the invention.

FIGS. 6A through 6E show the steps of establishing a coordinate systemfor the structuring fabric print.

FIGS. 7A, 7B, and 7C show the application of the analytic techniqueherein applied to a photograph of the knuckles of a fabric.

FIGS. 8A and 8B show an alternative analytic technique applied to aphotograph and print of the knuckles of a fabric.

FIG. 9 shows the application of the analytic technique to determine apocket surrounded by knuckles in a structuring fabric.

FIG. 10 shows the application of the analytic technique to determine thedepth of the pocket shown in FIG. 8.

FIGS. 11A and 11B show the application of the analytic techniquesapplied to an image of a paper product and its structuring fabric.

DETAILED DESCRIPTION OF THE INVENTION

My invention relates to apparatuses, processes, and systems fordetermining the characteristics of the contact surface of a fabric thatis used in a papermaking process. As will be apparent from thediscussion below, “characteristics of the contact surface of a fabric”refers to the characteristics of the contact surface that result fromthe knuckle and pocket configuration that makes up the contact surfaceof the fabric. In specific embodiments, my invention is adapted for usewith structuring fabrics that are used for three-dimensional structuringof a web in a papermaking process. Such structuring fabrics are oftenconstructed with yarns made from, for example, polyethyleneterephthalate (PET), polyester, polyamide, polypropylene, and the like.As will be further explained below, the particular contact surface of astructuring fabric will have a significant effect on the structure ofthe paper product, and my invention utilizes techniques forcharacterizing aspects of the contact surface. It should be noted,however, that my invention is applicable with any type of fabric that isused in a papermaking process, including fabrics that are used forpurposes other than structuring the web.

FIG. 1 shows an example of a through air drying (TAD) papermakingprocess in which a structuring fabric 48 is used to form thethree-dimensional structure of the paper product. To begin the process,furnish supplied through a head box 20 is directed in a jet into the nipformed between a forming fabric 24 and a transfer fabric 28. The formingfabric 24 and the transfer fabric pass between a forming roll 32 and abreast roll 36. The forming fabric 24 and transfer fabric 28 divergeafter passing between forming roll 32 and breast roll 36. The transferfabric 28 then passes through dewatering zone 40 in which suction boxes44 remove moisture from the web and transfer fabric 28, therebyincreasing the consistency of the web, for example, from about 10% toabout 25% prior to transfer of the web to structuring fabric 48. In someinstances, it will be advantageous to apply some amount of vacuum asindicated through vacuum assist boxes 52, in a transfer zone 56,particularly, when a considerable amount of fabric crepe is imparted tothe web in transfer zone 56 by a rush transfer wherein the transferfabric 28 is moving faster than the structuring fabric 48.

Because the web still has a high moisture content when it is transferredto the structuring fabric 48, the web is deformable such that portionsof the web can be drawn into pockets formed between the yarns that makeup the structuring fabric 48 (the formation of pockets in a fabric willbe described in detail below). As the structuring fabric 48 passesaround the through air dryers 60 and 64, the consistency of the web isincreased, for example, from about 60% to about 90%. The web is therebymore or less permanently imparted with a shape by the structuring fabric48 that includes domes where the web is drawn into the pockets of thestructuring fabric 48. Thus, the structuring fabric 48 provides athree-dimensional shape to the web that results in a paper producthaving the dome structures.

To complete the paper forming process, the web is transferred from thestructuring fabric 48 to the Yankee cylinder 68 without a majordegradation of its properties by contacting the web with adhesivesprayed onto Yankee cylinder 68 just prior to contact with thetranslating web. After the web reaches a consistency of at least about96%, light creping is used to dislodge the web from Yankee cylinder 68.

While FIG. 1 demonstrates one type of process in which a structuringfabric is used to impart a three-dimensional shape to a paper product,there are many other papermaking processes in which a structuring fabriccan be used to impart a three-dimensional structure to the paperproduct. For example, a structuring fabric may be used in a papermakingprocess that does not utilize through air drying (TAD). An example ofsuch a non-TAD process is disclosed in U.S. Pat. No. 7,494,563, thedisclosure of which is incorporated by reference in its entirety. Aswill be appreciated by those skilled in the art, the invention disclosedherein is not limited to being used in any particular papermakingprocess, but rather, may be applied to fabrics used in a wide variety ofpapermaking processes.

FIG. 2 is a view of a portion of the web facing side of a structuringfabric 200. The fabric 200 includes warp yarns 202 that would run in themachine direction (MD) when the fabric 200 is used in a papermakingprocess, and weft yarns 204 that run in the cross machine direction (CD)when the fabric 200 is used in a papermaking process. The warp and weftyarns 202 and 204 are woven together so as to form the structure offabric 200. It should be noted that, when looking down on FIG. 2, in theweb-contacting surface of the structuring fabric 200, some of thedepicted yarns 202 and 204 are below the plane that contacts the webduring the papermaking process, i.e., the contact surface of the fabric200. The upper-most points of the yarns 202 and 204 that define theplane of the contact surface are the knuckles 206 and 208. That is, theknuckles 206 and 208 form the actual contact surface of the formingfabric 200. Pockets 210 (shown as the outlined areas in FIG. 2) aredefined in the areas between knuckles 206 and 208. During a papermakingoperation, portions of the web can be drawn into the pockets 210, and itis the portions of the web that are drawn into the pockets 210 thatcorrespond to the domes in the finished paper product, as also describedabove.

It should be noted that a structuring fabric may not initially bemanufactured with knuckles, such as the knuckles 206 and 208 in FIG. 2.Instead, knuckles are often formed by sanding or grinding one of thesurfaces of the structuring fabric. Further, as the structuring fabricis used in a papermaking operation, wear on the surface of thestructuring fabric may further increase the length of the knuckles. Aswill be described below, the present invention provides for determiningcharacteristics of the knuckles, including characteristics of theknuckles as the fabric is subjected to wearing.

It should also be noted that a structuring fabric can take on numerousforms, depending on, for example, the weave pattern of the warp and weftyarns and the size of the yarns. The structuring fabric 200 depicted inFIG. 2 includes knuckles 206 that are formed on the warp yarns 202 andknuckles 208 that are formed on the weft yarns 204. This may haveresulted from the fabric 200 being sanded or worn to the point that theknuckles are formed on both the warp and weft yarns 202 and 204. Withless sanding, however, the fabric 200 might have only knuckles 206 onthe warp yarns 202, and not on knuckles 208 on weft yarns 204, or viceversa. Numerous configurations of weft and warp yarns in structuringfabrics are known in the art, and the numerous configurations allow fordifferently shaped paper products to be formed with the fabrics.

An apparatus and a technique for forming a print of the contact surfaceformed by the knuckles of a fabric is shown in FIGS. 3A and 3B. FIG. 3Ais a side view of a contact surface printing apparatus 300, and FIG. 3Bis a front view of the contact surface printing apparatus 300. Thisapparatus 300 includes a C-shaped frame structure 302 with first andsecond arms 303 and 305. A first plate 304 is movably supported by thefirst arm 303, and a stationary second plate 306 is supported by thesecond arm 305. A print of the knuckles of a fabric is formed betweenthe first and second plates 304 and 306, as will be described in detailbelow.

The first plate 304 is operatively connected to a hydraulic pump 308 foractuating movement of the first plate 304 towards the second plate 306.In some embodiments, hydraulic pump 308 is hand-operated, with a releasevalve for allowing the first plate 304 to be retracted from the secondplate 306. The pump 308, however, can take many other forms so as toeffect movement of the first plate 304. The pump 308 may be connected toa transducer and transducer indicator 310 for measuring the pressureapplied by the pump 308 to the first plate 304 as the first plate 304 ispressed against the second plate 306. As a specific example, an ENERPAC®Hydraulic Hand Pump Model CST-18381 by Actuant Corp. of Milwaukee, Wis.,can be used. As a specific example of the pressure transducer, aTransducer Techniques Load Cell Model DSM-5K with a correspondingindicator, made by Transducer Techniques, Inc., of Temecula, Calif., canbe used. Of course, in other embodiments, the pump 308 and transducerand transducer indicator 310 may be combined into a single unit.

The frame 302 of the contact surface printing apparatus 300 includeswheels 312 adjacent to the front end of the frame 302, as well as amount 313 that may be used to hold the pump 308 and/or transducer 310.One or more wheels provided to the frame 312 make the frame 302 easierto move. An advantageous feature of the contact surface printingapparatus 300, according to embodiments of the invention, is itsportability. For example, with a configuration as shown in FIGS. 3A and3B, the print apparatus 300 may be easily moved about sections of afabric that is mounted on a papermaking machine. As will certainlybecome appreciated by those skilled in the art, the ability to formprints of the contact surface of a fabric while the fabric is mounted toa papermaking machine, and, thus, characterize the fabric according tothe techniques described below, provides numerous benefits. As but oneexample, the wearing of a fabric on a papermaking machine can easily bemonitored by using the contact surface printing apparatus 300 so to takeprints of the knuckles of the fabric after different periods ofoperation of the papermaking machine.

While the contact surface printing apparatus 300 shown in FIGS. 3A and3B includes a frame structure 302 that connects the first and secondplates 304 and 306, in other embodiments, a contact surface printingapparatus may not include such a single frame structure 302. Instead,the first and second plates 304 and 306 may be non-connected structuresthat are individually aligned to form the print of a fabric. In stillother embodiments, the plates 304 and 306 may take vastly differentforms from those depicted in FIGS. 3A and 3B. For example, one of theplates 304 and 306 could be formed as an extended surface, while theother plate is formed as a circular structure that is rolled across theextended surface. The term “plate,” as used herein, is a broad term thatencompasses any structure sufficient for contacting and/or supportingthe components for making the print of the fabric. Additionally, as isclear from the description above, the relative motion of the first andsecond plates 304 and 306 in any embodiment could be reversed, such thatthe second plate 306 is made movable while the first plate 304 is heldstationary.

FIG. 4 is a detailed view of Section A of the contact surface printingapparatus 300 shown in FIG. 3A, with the apparatus 300 being set up tomake a print of a section of a fabric 312. The fabric 312 is positionedbetween the plates 304 and 306, and a strip of pressure measurement film314 is positioned against the structuring fabric 312. Between thepressure measurement film 314 and the first plate 304 is one or moresheets of paper 316. Between the fabric 312 and the second plate 306 isa strip of rubber 318.

Pressure measurement film is a material that is structured such that theapplication of force upon the film causes microcapsules in the film torupture, producing an instantaneous and permanent, high-resolution imagein the contacted area of the film. An example of such a pressuremeasurement film is sold as Prescale film by Fujifilm HoldingsCorporation of Tokyo, Japan. Another example of pressure measurementfilm is PRESSUREX-MICRO® by Sensor Products, Inc., of Madison, N.J.Those skilled in the art will recognize that other types of pressuremeasurement films could be used in the printing techniques describedherein. In this regard, it should be noted that for the analysistechniques described below, the pressure measurement film need notprovide an indication of the actual pressure applied by the fabric tothe film, but rather, the pressure measurement film need only provide aprint image showing the contact surface formed by the knuckles of afabric.

The pressure applied to plate 304 when forming a print of fabric 310 onpressure measurement film 314 can be selected so as to simulate thepressure that would be applied to a web against the fabric 312 in anactual papermaking process. That is, the pump 308 may be used togenerate a pressure (as measured by transducer 310) on the plate 304that simulates the pressure that would be applied to a web against thefabric 312 in a papermaking process. In the papermaking processdescribed above in conjunction with FIG. 1, the simulated pressure wouldbe the pressure that is applied to the web against the fabric 48 to theYankee cylinder 68. In some papermaking processes, such as the processdescribed in aforementioned U.S. Pat. No. 7,494,563, the pressureapplied to the web against the fabric is generally in the range of sixhundred psi. Accordingly, to simulate this papermaking process, sixhundred psi of pressure would be applied by the hydraulic pump 308 tothe plate 304 when forming the image of the knuckles of fabric 312 inthe pressure measurement film 314. For such an operation, it has beenfound that medium pressure 10-50 MPa Prescale film by FujiFilm canprovide a good image of the knuckles of a structuring fabric.

Referring again to FIG. 4, the paper 316 acts as a cushion to improvethe print of the fabric 312 formed on the pressure measurement film 314.That is, paper 316 provides compressibility and a smooth surface, suchthat the knuckles of the fabric 312 may “sink” into the pressuremeasurement film 314, which, in turn, forms a high resolution image ofthe knuckles in the film 314. To provide these properties, constructionand kraft are examples of types of paper that could be used for thepaper 316.

The strip of rubber 318 creates a level contact surface for supportingthe fabric 314. In embodiments of the invention, the plates 304 and 306are made of a metallic material, such as steel. A steel plate would mostlikely have imperfections that reduce the quality of the print of theknuckles of the fabric formed in the pressure measurement paper 316. Thepaper 316 and the rubber 318 that are used between the plates 304 and306, and the pressure measurement film 314 and the fabric 312, however,provide more level contact surfaces than the surfaces of the metallicplates 304 and 306, thereby resulting in better images being formed inthe pressure measurement film 314. Those skilled in the art willrecognize that other materials as alternatives to the paper 316 andrubber 318 may be used as structures to provide the level surfacesbetween the plates 304 and 306 of the apparatus 300.

In other embodiments, a print is made of the knuckles of a fabric inmaterials other than pressure measurement film. Another example of amaterial that can be used to form prints of a film is wax paper. A printof the contact surface of a fabric may be made in a wax surface bypressing the contact surface of a fabric against wax paper. The print inthe wax paper could be made using the plates 304 and 306 in the printforming apparatus 300 described above, or with other configurations ofthe plates. The wax paper print can then be analyzed in the same manneras a pressure measurement film print, as will be described below.

FIGS. 5A through 5D show examples of prints of knuckles formed inpressure measurement film using the contact surface printing apparatus300. In these prints, the distinctive shapes and patterns of theknuckles of the fabrics can be seen. As discussed above, the knucklesform the contact surface for the fabric. Hence, high resolution printsof the knuckles in a pressure measurement film, such as those shown inFIGS. 5A through 5D, provide an excellent representation of the contactsurface of a fabric.

Next, a system for analyzing the prints of knuckles, such as those shownin FIGS. 5A through 5D, will be described. In the system, graphicalanalysis will be conducted on a conventional computer system. Such acomputer system will include well-known components, such as at least onecomputer processor (e.g., a central processing unit or a multipleprocessing unit) that is connected to a communication infrastructure(e.g., a communications bus, a cross-over bar device, or a network). Afurther component of the computer system is a display interface (orother output interface) that forwards video graphics, text, etc., fordisplay on a display screen. The computer system may still furtherinclude such common components as a keyboard, a mouse device, a mainmemory, a hard disk drive, a removable-storage drive, a networkinterface, etc.

As a first step in the analysis, a print of the contact area of theknuckles of a fabric is converted to a computer readable image using aphoto scanner. Any type of photo scanner may be used to generate thecomputer readable image. In certain embodiments, however, a photoscanner having at least 2400 dpi has been found to provide a good imagefor analysis. With the resolution of the scan of the image, an imaginganalysis program (as will be described below) can apply an exact scaleto the image. As will be described below, the exact scaling will be usedin the calculation of the surface characteristics of the structuringfabric.

The scanned image may be stored in a non-transitory computer-readablemedium in order to facilitate the analysis described below. Anon-transitory computer readable medium, as used herein, comprises allcomputer-readable media except for a transitory, propagating signal.Examples of non-transitory computer readable media include, for example,a hard disk drive and/or a removable storage drive, representing a diskdrive, a magnetic tape drive, an optical disk drive, etc.

The scanned image, as well as characteristics of the contact surfacescanned image that are determined according to the techniques describedbelow, may be associated with a database. A “database,” as used herein,means a collection of data organized in such a way that a computerprogram may quickly select desired pieces of the data, e.g., anelectronic filing system. In some implementations, the term “database”may be used as shorthand for “database management system.”

In order to perform quantitative analysis of the scanned print image, animage analysis program is used with the scanned images of the knucklesof a fabric. Such an image analysis program is developed, for example,with computational software that works with graphical images. Oneexample of such computational development software is MATHMATICA® byWolfram Research, LLC, of Champaign, Ill. As will be described below,the image analysis program will be used to specifically identify theknuckles in the fabric print image of the structuring fabric, and, withknown scaling of the fabric print image, the image analysis program cancalculate the sizes of the knuckles and estimate sizes of the pockets.

When analyzing the scanned image, any size area that includes aplurality of knuckles and a pocket could be used for the analysisdescribed below. In specific embodiments, it has been found that a 1.25inch by 1.25 inch area of an image of a fabric allows for a goodestimation of properties, such as pocket sizes using the techniquesdescribed herein. In particular, it has been found that when an image isformed with a 2400 dpi resolution (discussed above), and using a 1.25inch by 1.25 inch area of an image for the analysis, a goodcharacterization of the contact surface can be conducted. Of course,other resolutions and/or area may also provide good results.

FIG. 6A through 6E depict the steps of identifying the knuckles in amagnified portion of the scanned image of a print using the imageanalysis program. Initially, as shown in FIG. 6A, a magnified portion ofan image 600 is viewed on the display screen of the computer systemrunning the analysis program. The image 602, which may be formed usingthe print technique described above, shows the knuckles 602. Along withusing the image 600 with the analysis program, the scaling of the image600 can be input into an analysis program. Such a scaling may be input,for example, as 2400 dpi, from which the analysis program can apply thescale SC to the image 600. The analysis program will then use the scaleto calculate the sizes and positions of the knuckles, as describedbelow.

FIGS. 6B and 6C shows steps for identifying a specific knuckle 602Ausing the analysis program. The knuckle 602A is initially selected basedon its location at a center region of the magnified image 600. In thisstep, a rough outline of the knuckle 602A is applied. The rectangularbox 604, which may be a stored shape in the analysis program, isinitially applied around the knuckle 602A in order to initiate theknuckle identification process. The initial rectangular box 604 shapemay then be more closely refined to match the shape of the knuckle 602A,as shown in FIG. 6C. In this case, the ends 606 and 608 are reshaped tobe more rounded, and, thus, more closely correspond to the ends of theknuckle 602A. Although not shown, further refinements could be made tothe outline of the knuckle 602A until a sufficient match is made. Suchrefinements might be conducted by further magnifying the image 600.

As shown in FIG. 6D, after the knuckle 602A is identified by theoutline, guidelines 610 and 612 are drawn. The guidelines 610 and 612are each drawn so as to pass through the center of the knuckle 602A, andextend in straight lines through the centers of the other knuckles.Notably, the guidelines 610 and 612 are also drawn so as to not crossthe areas where pockets are formed in the fabric, which are known tocorrespond to the areas between groups of knuckles. By drawing theguidelines 610 and 612 straight between the centers of the knuckles, theguidelines 610 and 612 do not cross the area of the pockets that areformed between the knuckles.

After the guidelines 610 and 612 are drawn, as shown in FIG. 6E, furtherguidelines are drawn. These guidelines are drawn in a similar manner toguidelines 610 and 612, i.e., through the centers of the knuckles andnot passing through areas where pockets are formed. To aid in theprocess of drawing the guidelines, a lower magnification may be used.With the guidelines, a coordinate system is, in effect, established forthe positions of the knuckles. The analysis program, therefore, can nowidentify the size and shape of the knuckles based on the outline 602A,and can identify the locations of the knuckles as determined by thepoints wherein the guidelines cross. The analysis program further hasthe scale SC of the image 600 input. It follows that the analysisprogram can apply the scale to the outline knuckle 602A and the knucklepositioning to calculate the actual sizes and spacing of the knuckles.Note as well that the analysis program may calculate the frequency ofthe guidelines such as the number of times that the guidelines 612 crossguideline 610 per a unit length. The frequency of each set of theguidelines 610 and 612 will be used in calculations of properties of thefabric, and in other aspects of the invention, as will be describedbelow.

It should be noted that, as shown in FIGS. 6D and 6E, the knuckles areall about the same size and all about the same shape, and the knucklesare regularly spaced along the guidelines. This is not surprisinginasmuch as most fabrics for papermaking machines are manufactured withhighly consistent yarn patterns, which results in consistent knucklesizes and positions. The consistency in size, shape, and placement ofthe knuckles allows for accurate estimates of the size and shapes of allthe knuckles on the contact surface of a fabric based on a singleselected knuckle, or on a limited number of identified knuckles, and aclose estimate of the sizes and locations of the knuckles can beachieved without identifying each knuckle. Of course, to achieve evenfurther accuracy, more than one knuckle could be identified, and theoutlines and guidelines could be drawn at different portions of animage.

As shown in FIG. 6E, the guidelines 610 and 612 define a plurality ofunit cells. A particular unit cell 613 is shown between guidelinesegments 610A, 610B, 612A, and 612B. The unit cell 613, in effect,demonstrates the minimum repeating pattern in the fabric, and themaximum allowable pocket size. It should be noted while the fabric shownin FIGS. 6A through 6E has about one warp knuckle per unit cell, otherfabrics may have more than one warp knuckle and/or more than one weftknuckle per unit cell. In other words, the unit cells defined by knucklepatterns will vary with different fabric patterns.

As will be readily apparent to those skilled in the art, any or all ofthe steps shown in FIGS. 6A through 6E can either be performed by a useron a display screen, or alternatively, may be automated so as to beperformed upon execution of the analysis program. That is, the analysisprogram may be configured to automatically identify knuckles as thedarkened regions of images, outline the knuckles, and then draw theguidelines based on the identified knuckles in the manner describedabove.

After the selected knuckle has been identified, and after the guidelinesare established through the knuckles, multiple properties of the fabricmay be calculated using knuckle sizes and positions determined by theanalysis program. To perform such calculations, the knuckle size andpositioning data can be exported from the analysis program to aconventional spreadsheet program to calculate the properties of thefabric. Examples of the determinations made by the analysis program andthe calculations that follow from such determinations are shown in Table1.

TABLE 1 Characteristic of the Fabric Determination/Calculation KnuckleLength (KL) determined based on outline of identified warp knuckle oridentified weft knuckle Knuckle Width (KW) determined based on outlineof identified warp knuckle or identified weft knuckle Frequency ofGuidelines (f) determined based on guidelines drawn through knucklesfreq 1 = frequency of the first set of parallel lines (per inch or cm)freq 2 = frequency of the second set of parallel lines (per inch or cm)Rounding Radius (r) determined based on outline of identified warpknuckle and/or identified weft knuckle, the rounding radius is the levelof rounding that is application to the corners of rectangular objectsKnuckle Density Per Unit Cell determined based on the number of warp or(KDUC) (knuckles per unit cell) weft knuckles identified within a cellUnit Cell Knuckle Area (UKA) warp UKA = warp KW × warp KL − ((2 × warpr)² − π(warp r)²) weft UKA = weft KW × weft KL − ((2 × weft r)² − π(weftr)²) Knuckle Density (KD) F = freq 1 × freq 2 warp KD = F × warp KDUCweft KD = F × weft KDUC Total Warp or Weft Knuckle warp area % = warp KD× warp UKA Contact Area (%) weft area % = weft KD × weft UKA Total %In-Plane Knuckle Contact TKCA = warp area % + weft area % Area % AreaContribution (AC) % warp AC = [warp UKA/(warp UKA + weft UKA)] × 100 %weft AC = [weft UKA/(warp UKA + weft UKA)] × 100 Pocket Area Estimate(PA) PA = (1/(freq 1 × freq 2)) − (warp UKA × warp KDUC) − (weft UKA ×weft KDUC) Pocket Density (PD) (pockets per PD = freq 1 × freq 2 squareinch or centimeter)

The fabric from which image 600 was obtained only included knuckles 602on the warp threads. Other fabrics, however, may include knuckles on theweft threads, such as the fabrics that formed the prints in FIGS. 5B and5D. With such fabrics, the knuckles on the weft threads can beidentified using the outlining technique described above, and theguidelines can be drawn through the weft knuckles using the techniquedescribed above.

While the contact surface of a fabric may be characterized by using aprint of the knuckles of the fabric that is formed, for example, by thecontact surface printing apparatus 300, in other embodiments, an imageof the contact surface of the fabric may be obtained in a differentmanner. An alternative to forming a print of the knuckles of the fabricis to photograph the knuckles of a fabric, and then use theabove-described procedures and techniques for analyzing an image formedfrom the photograph. In this regard, a photograph with 2400 dpi has beenfound to provide sufficient high and low resolution so as to be analyzedby the techniques described herein.

An example of a photograph 700 of the portion of a papermaking fabricwith knuckles 702 a is shown in FIG. 7A, and the application of theabove-described analytic technique to the image generated fromphotograph 700 is shown in FIGS. 7B and 7C. The photograph 700 in FIG.7A shows the fabric 701 next to a ruler R. When the photograph isconverted to an image for use with the analysis program, the scale forthe image 700A can be input based on the photographed ruler R. That is,ruler R in the image 700A provides an input from which the analysis canapply a scale to the image. The displayed image 700A, along with thescale SC, is shown in FIG. 7B.

To identify the sizes and locations of knuckles in an image obtainedfrom a photograph of the fabric, the same techniques described abovewith an image from a print of the fabric, may be used. For example, anoutlined knuckle 702A and guidelines 710 and 712 are shown on the image700A in FIG. 7C. With the knuckle sizing and location data from theanalysis program, all of the above-described calculations may be carriedout to characterize the contact surface of the fabric 700 that wasphotographed.

Table 2 below shows the results of the calculations of surfacecharacteristics for a fabric, with one set of calculations being derivedfrom a print of the fabric, and a second set calculations being derivedfrom a photograph of the fabric.

TABLE 2 Photograph of Print of fabric fabric Warp Contact Length (mm)1.27 1.27 Knuckles Contact Width (mm) 0.28 0.28 Percent Warp Contact19.9 20.5 Weft Contact Length (mm) 0.58 0.58 Knuckles Contact Width (mm)0.38 0.38 Percent Weft Area 11.2 11.5 Total In-Plane Total Contact Area31.1 32.0 Contact Percent Warp- Warp Area (%) 64 64 Weft Ratio Weft Area(%) 36 36 Pocket (1/cm²) 58.4 60.2 Density Fabric Cell Freq. 1 (1/cm)7.7 7.7 Definition Freq. 2 (1/cm) 7.6 7.8

The results shown in Table 2 demonstrate that the contact surfacecharacterization calculations achieved using the photograph techniqueclosely correspond to the calculations achieved using the print of thefabric.

The above-described techniques provide a good estimate of the propertiesof a fabric, particularly when the shapes of the unit cells formed bythe guideline segments are substantially rectangular. In cases, however,where the shapes of the unit cells formed by the guidelines arenon-rectangular, parallelograms, an alternative technique may be used toprovide more accurate estimates of the properties of the fabrics. Anexample of this alternative technique is shown in FIG. 8A, which is animage generated from a photograph of the surface of a fabric using theabove described image analysis program. In this figure, a unit cell 813is defined by the guideline segments 810A, 810B, 812A, and 812B. Theunit cell 813 formed by the guideline segments 810A, 810B, 812A, and812B is a substantially non-rectangular, parallelogram shape. In thisparallelogram, an angle θ is defined at the corner A where guidelinesegments 810A and 812B intersect, and the angle θ is also defined at thecorner B where the guideline segments 810B and 812A intersect. Thisangle θ can be readily determined using the image analysis program basedon the difference in orientation angles of the guidelines. Further, theimage analysis program can also determine the distance between theguideline segments 810A and 810B (“DIST 1”) and the distance betweenguideline segments 812A and 812B (“DIST 2”) based on the scale of theimage in the manner generally described above. Having determined theintersecting angle θ, the DIST 1, and the DIST 2, the area of the unitcell (UCA) can be calculated using either of the Formula (1) or Formula(2):

UCA=(DIST 1/sin θ)×DIST 2   (1)

UCA=(DIST 2/sin θ)×DIST 1   (2)

Formulas (1) and (2) are derived from the standard formula forcalculating the area of a parallelogram, namely Area=base length×height,where DIST 1 or DIST 2 is used as the height of the parallelogram, andthen base length is calculated from the sine of the angle θ and theother of DIST 1 or DIST 2.

Table 3 shows examples of determinations made by the analysis programand the calculations that follow from such determinations when using thealternative technique based on a non-rectangular, parallelogram unitcell area calculation.

TABLE 3 Characteristic of the Fabric Determination/Calculation KnuckleLength (KL) determined based on outline of identified warp knuckle oridentified weft knuckle Knuckle Width (KW) determined based on outlineof identified warp knuckle or identified weft knuckle Frequency ofGuidelines (f) determined based on guidelines drawn through knucklesfreq 1 = frequency of the first set of parallel lines (per inch or cm)freq 2 = frequency of the second set of parallel lines (per inch or cm)Intersecting Angle of the determined based on guidelines drawn throughGuidelines (θ) knuckles θ1 = orientation angle of the first set ofparallel lines (degree) θ2 = orientation angle of the second set ofparallel lines (degree) θ = Abs (θ1 − θ2): intersecting angle betweenthe two sets of guidelines Rounding Radius (r) determined based onoutline of identified warp knuckle and/or identified weft knuckle, therounding radius is the level of rounding that is application to thecorners of rectangular objects Knuckle Density Per Unit Cell determinedbased on the number of warp or (KDUC) (knuckles per unit cell) weftknuckles identified within a cell Unit Cell Knuckle Area (UKA) warp UKA= warp KW × warp KL − ((2 × warp r)² − π(warp r)²) weft UKA = weft KW ×weft KW − ((2 × weft r)² − π(weft r)²) Knuckle Density (KD) warp KD = PD× warp KDUC weft KD = PD × weft KDUC Total Warp or Weft Knuckle warparea % = warp KD × warp UKA Contact Area (%) weft area % = weft KD ×weft UKA Total % In-Plane Knuckle Contact TKCA = warp area % + weft area% Area % Area Contribution (AC) % warp AC = [warp UKA/(warp UKA + weftUKA)] × 100 % weft AC = [weft UKA/(warp UKA + weft UKA)] × 100 PocketArea Estimate (PA) PA = (1/PD) − (warp UKA × warp KDUC) − (weft UKA ×weft KDUC) Pocket Density (PD) (pockets per PD = freq 1 × [freq 2 × sinθ] square inch or centimeter)

It should be noted that, while some of the characteristics in TABLE 3are determined or calculated in the same manner as those described abovein TABLE 1, the knuckle density, the total warp or weft knuckle contactarea, the contact area ratio, the percent area contribution, the pocketarea estimate, and the pocket density characteristics are calculateddifferently in TABLE 3 than in TABLE 1. By accounting for thenon-rectangular, parallelogram shape of the unit cells, these differentcalculations provide for more accurate estimations of thecharacteristics of fabrics that have non-rectangular, parallelogramshaped unit cells.

FIG. 8B is a print of a fabric made with the above-described techniques.In this case, the fabric has very non-rectangular unit cells, with oneof the angles θ at the corners of the parallelograms defining the unitcells being about 140 degrees. In order to demonstrate the differencebetween the first techniques described, which are not specificallyadapted for parallelogram shaped unit cells, and the technique for anon-rectangular, parallelogram unit cells, two sets of calculations wereperformed on the fabric, with the results being shown in TABLE 4.

TABLE 4 Without With Parallelogram Parallelogram Calculation CalculationWarp Contact Length (mm) 0.00 0.00 Knuckles Contact Width (mm) 0.00 0.00Percent Warp 0.0 0.0 Contact Area Weft Contact Length (mm) 1.98 1.98Knuckles Contact Width (mm) 0.28 0.28 Percent Weft 25.4 16.5 ContactArea Total In-Plane Total Contact Area 25.4 16.5 Contact Percent Warp-Warp Area (%) 0.0 0.0 Weft Ratio Weft Area (%) 100.0 100.0 Pocket(1/cm²) 47.3 30.7 Density Fabric Cell Freq. 1 (1/cm) 5.7 5.7 DefinitionFreq. 2 (1/cm) 8.3 8.3

It should be noted that, while some of the properties shown in TABLE 4are the same for the two calculations, the total in-plane contact areaand the pocket density are different. Given that the calculation methodadapted for non-rectangular, parallelogram unit cells utilizesmeasurements that more closely matches the actual underlying shape andstructure of the fabric shown in FIG. 8B, it follows that the totalin-plane contact area (i.e., the percentage of the fabric thatcorresponds to knuckles) and the pocket density determined with thecalculation technique specifically adapted for non-rectangular,parallelogram unit cells are more accurate. And, as those skilled in theart will appreciate, the total in-plane contact area and the pocketdensity of a fabric significantly affect the paper-making properties ofa fabric. Thus, the non-rectangular, parallelogram calculations providemore accurate estimations for important properties of a fabric.

Another important characteristic of a papermaking fabric is the depth towhich the web can be drawn into pockets in the fabric during thepapermaking process. As discussed above, domes are formed in final paperproducts that correspond to the portions of the web that were drawn intothe pockets in the fabric. Hence, the pocket depth of a papermakingfabric directly affects the paper product formed using the fabric.Techniques for determining the pocket depth of a fabric will now bedescribed.

FIG. 9 shows a magnified photograph of a structuring fabric. With thephotograph, and using the image analysis program described above, fourknuckles K1 to K4 are identified. A parallelogram has been drawn in amanner that connects the knuckles K1 to K4, with the lines of theparallelogram being drawn to not pass through the pocket area that isformed between the knuckles K1 to K4. With the parallelogram drawn, aprofile direction line PL can be drawn that passes from the knuckle K1,through the center of the pocket, to knuckle K3. The profile directionline PL will be used to determine the pocket depth using a depthmeasurement instrument, as described below. Note that the profiledirection line PL from knuckle K1 and knuckle K3 passes through thecenter of the pocket. As will be described below, the pocket depth of astructuring fabric is determined as the depth in the pocket to which thecellulosic fibers could penetrate in the paper making process. In thecase of the fabric shown in FIG. 9, the maximum fiber migration depth isat the center of the pocket. It follows that a profile direction linecould alternatively be drawn from knuckle K2 to knuckle K4 passingthrough the center of the pocket, and the alternative profile directionline could be used for the pocket depth determination described below.Those skilled in the art will also recognize that different structuringfabrics will have different configurations of knuckles and pockets, buta profile direction line could easily be determined for differentstructuring fabrics in the same manner as the profile direction line isdetermined as shown in FIG. 9.

FIG. 10 is screenshot of a program used to determine the profile of apocket of the structuring fabric shown in FIG. 9. The screenshot wasformed using a VHX-1000 Digital Microscope manufactured by KeyenceCorporation of Osaka, Japan. The microscope was equipped with VHX-H3Mapplication software, also provided by Keyence Corporation. Themicroscopic image of the pocket is shown in the top portion of FIG. 10.In this image, the knuckles K′1 and K′3 and the pocket between theknuckles can easily be seen. A depth determination line DL has beendrawn from point D to point C, with the depth determination line DLpassing through the knuckles K′1 and K′3 and through the center of thepocket. The depth determination line DL is drawn to closely approximatethe profile determination line PL that is shown in FIG. 8. That is,based on inspection of the depth determination line DL derived using theknuckle and pocket image shown in FIG. 9, a user can draw the depthdetermination line DL in the microscopic image shown in FIG. 10, withthe depth determination line DL passing through the areas thatcorrespond to the knuckles K′3 and K′1 and the center portion of thepocket.

With the depth determination line DL drawn, the digital microscope canthen be instructed to calculate the depth profile of the pocket alongthe depth determination line DL, as is shown in the bottom portion ofFIG. 10. The profile of the pocket is highest at the areas correspondingto the knuckles K′3 and K′1, and the profile falls to its lowest pointat the center of the pocket. The pocket depth is determined from thisprofile as starting from the height of the knuckles K′3 and K′1, whichis marked by the line A on the depth profile. As with any two knucklesof a structuring fabric measured to this degree of precision, theknuckles K′3 and K′1 do not have the exact same height. Accordingly, theheight A is determined as an average between the two heights of theknuckles K′3 and K′1. The pocket depth is determined as ending at apoint just above the lowest point of the depth profile, marked by theline B on the depth profile. As those skilled in the art willappreciate, the depth of the pocket from line A to line B approximatelycorresponds to the depth in the pocket to which the cellulosic fibers inthe web can migrate in a papermaking process. Note that the VHX-H3Msoftware (discussed above) forms the full depth profile from a pluralityof slices in the thickness direction of the fabric. Also, note that informing the depth profile, the VHX-H3M software employs a filteringfunction to smooth the depth profile formed from the thickness slices.It should be noted that the measured pocket depth will slightly varyfrom pocket to pocket in a fabric. We have found, however, that anaverage of five measured pocket depths for a structuring fabric providesa good characterization of the pocket depth.

While a digital microscope is used in the above-described embodiments todetermine the pocket depth, other instruments may alternatively be usedto determine pocket depth with the techniques described herein. Forexample, in other embodiments, a laser profilometer (or “laserprofiler”) may be used to determine pocket depth in a similar manner asthe above-described digital microscope. A laser profiler can determine adepth profile of a pocket that can be used to determine the pocket depthin the same manner as the depth profile generated using the digitalmicroscope is used to determine pocket depth, as described above. Anexample of such a laser profiler is a TALYSURF® CLI high-resolution 3Dsurface profiling system manufactured by Taylor Hobson, Ltd., ofLeicester, United Kingdom. In still other embodiments, an inline laserprofile measurement device (“laser line scanner”) may be used todetermine the pocket depth of a fabric with the techniques describedherein. An example of such a laser line scanner is an LJ-V7000 serieshigh-speed inline profile inspection device manufactured by KeyenceCorporation.

When using a laser profiler or a laser line scanner, the same steps fordetermining the pocket depth may be used as are described above inconjunction with a digital microscope. That is, as shown in FIG. 9, theknuckles and a pocket are determined based on a representation of thesurface of a structuring fabric. The laser profiler or laser linescanner is then set to determine a depth profile across the pocket fromone knuckle to another knuckle, i.e., the laser profiler or laser linescanner scans across the line oriented as the line PL in FIG. 9. Fromthis measured profile, the pocket depth can be determined in ananalogous manner to that method described above in conjunction with FIG.10. For performing analysis of the depth profile measured by the laserprofiler or laser scanner, various analytic software programs may beused. One example is surface metrology software provided by TrueGage ofNorth Huntingdon, Pa.

Each of the alternative depth measurement instruments, i.e., digitalmicroscope, laser profiler, or laser line scanner, may offer certainadvantages. For example, a digital microscope might provide a highlyprecise measurement of pocket depth. On the other hand, a laser profileris generally an easy instrument to work with, and thereby can provide aquick measurement of pocket depth. As another example, a laser linescanner has the ability to quickly collect large volumes of data, and,thus, measure many depth profiles in a short period of time. In thisregard, an embodiment of my invention includes using a laser linescanner to determine pocket depth profiles of a structuring fabric thatis running on a papermaking machine. In this embodiment, the laser linescanner is positioned adjacent to the structuring fabric on the machine,with the laser line scanner measuring the pocket depth profiles as thefabric travels past the scanner. As will be appreciated by those skilledin the art, a structuring fabric in a papermaking machine may travel atspeeds greater than 3,000 feet per minute. Yet, a laser line scanner,such as the aforementioned LJ-V7000 series inspection system by KeyanceCorporation, has the ability to measure thousands of depth profiles persecond. Accordingly, a laser line scanner has the ability to measure thepocket depth in the quickly moving structuring fabric, thereby providinghighly useful pocket depth data while the structuring fabric is inactual use on a papermaking machine.

It should be noted that, regardless of the measurement instruments andtechnique used to determine pocket depth, the measured pocket depth willslightly vary from pocket to pocket in a fabric. I have found that,generally speaking, an average of five measured pocket depths for astructuring fabric provides a good characterization of the pocket depth.Of course, more or fewer measure measurements can be performed todetermine an average pocket depth depending, for example, on the levelof accuracy desired in the measurement.

In the pocket depth determination techniques described above, thestructuring fabric itself is used to determine the pocket depth. In somecases, it may be easier to form a representation of the fabric, and thendetermine the pocket depth from the representation. For example, arepresentation of the knuckle and pocket structure of a fabric can beformed by pressing the contact surface of a fabric against wax paper, asis also described above. The wax representation of the fabric can thenbe scanned using one of the above-described techniques. For example, alaser line scanner can be used to determine the depth in the wax printbetween the knuckles in the wax print.

Those skilled in the art will recognize that the effective volume of thepockets of a structuring fabric is an important property of astructuring fabric that can easily be determined once the pocket size iscalculated according to one of the above-described techniques. Theeffective volume of a pocket is the product of the cross-sectional areaof the pocket at the surface of the structuring fabric (i.e., betweenthe knuckle surfaces) multiplied by the depth of the pocket into whichcellulosic fibers in the web can migrate during the papermaking process.The cross-sectional area of the pockets is the same as the estimate ofthe pocket area (PA), as described in TABLE 1 or TABLE 2 above. Thus,the effective pocket volume may be calculated simply as the product ofthe pocket area estimate and the measured pocket depth.

Another important property of a structuring fabric may be defined as aplanar volumetric index for the fabric. Generally speaking, thesoftness, absorbency, and caliper of paper products made using a fabricmay be influenced by the contact area of the fabric, that is, the areaformed by the knuckle surfaces of the fabric that the web contacts inthe papermaking process. Further, the softness, absorbency, and caliperof the paper products may be influenced by the size of the pockets inthe fabric. The planar volumetric index provides an indication of thecontact area and pocket size, as the planar volumetric index iscalculated as the contact area ratio (CAR) (as set forth in TABLE 1 orTABLE 2 above) multiplied by the effective pocket volume (EPV)multiplied by one hundred, i.e., CAR×EPV×100. The contact area ratio andthe effective pocket volume may be calculated using the techniquesdescribed above, and thereafter the planar volumetric index for thefabric may easily be calculated.

As will certainly be appreciated by those skilled in the art, knowingcharacteristics of the knuckles and pockets of a fabric, such as knuckleand pocket sizes and densities, provides a deep understanding of thefabric. One example of the application using the characteristicsinvolves developing correlations between certain contact surfacecharacteristics and resulting paper products. With the correlations,further fabric configurations can be developed, and those configurationscan be characterized without testing a full-scale fabric on apapermaking machine. Thus, the techniques described above fordetermining contact surface characteristics of a fabric may save timeand resources for both fabric manufacturers and/or paper producers thatare experimenting with different fabrics.

The above-described techniques can also be used in methods of analyzingthe wear on a papermaking fabric. In one such method, a firstrepresentation of the knuckles in a portion of the fabric is formed in amedium. This first representation may be a print on a pressuremeasurement film, or the representation may be a photograph of a portionof the fabric and stored in a camera. A first image is generated of theknuckles of the fabric based on the first representation, such as byscanning the pressure measurement film or downloading the photographfrom the camera. From the generated image, at least one characteristicrelated to the contact area of the fabric may be determined as describedabove. The fabric may then be subjected to wearing. If the fabric ismounted on a papermaking machine, the wearing may come about simply byoperating the papermaking machine. Alternatively, a simulated wearingmay be performed on the fabric by sanding or grinding.

After the fabric is worn, the process of obtaining an image of a portionof the fabric and determining contact surface characteristics is againperformed. That is, a second representation of the knuckles in theportion of the fabric is formed in a medium, which is used to generate asecond image, which in turn is analyzed to determine the surfacecharacteristics of the film. In this regard, the second representationmay or may not be taken from the same portion of the fabric as the firstrepresentation. It would be expected that knuckles in the fabric wouldincrease in size as a result of the wearing. Further, new knuckles maybe formed in the fabric. As part of the contact surfacecharacterization, increases in the knuckle sizes can be quantified bycomparing the analysis of the second image after wearing and the firstimage before wearing. Such a process of wearing the fabric andthereafter determining the contact surface characteristics may berepeated any number of times, and with any given amount of wearingbetween each analysis.

A further part of analyzing the wear on the fabric includes correlatingthe paper products made using the fabric with the changes in the contactsurface due to the wearing. For example, before the first representationis taken of the fabric, a paper product is formed using the fabric.Properties of the paper product, such as the size of domes in theproduct or the caliper of the product, are then correlated with thecontact surface characteristics determined through analysis of the firstimage formed by the first representation. A second paper product is thenformed using the fabric, after the fabric is subject to wearing andbefore the second representation is taken of the fabric. Properties ofthe second-formed paper product are then correlated with the contactsurface characteristics determined through analysis of the second image.Thus, an understanding can be achieved of how the formed paper productchanges as the particular fabric configuration is worn.

In further aspects of the invention, the above-described techniques andprocesses may be used to compare different portions of a fabric,particularly, after the fabric runs on a papermaking machine overperiods of time. It is known that different portions of a fabric willoften show different wearing due to inconsistencies in the track thatthe fabric follows in the papermaking machine. According to differentembodiments, the surface characterization techniques can be applied, forexample, to different portions of a fabric before and after the fabricis run on a papermaking machine. Alternatively, the surfacecharacterization techniques can be applied to different portions of thefabric while the fabric is still mounted on the papermaking machine.Thus, an understanding can be achieved of how different portions of afabric are worn in a papermaking machine.

According to yet another aspect of the invention, the contact surfacecharacterization can be used to obtain a fabric for making a paperproduct with a particular three-dimensional structure. FIGS. 11A and 11Bdemonstrate such a process. FIG. 11A shows an example of an image 800 ofa paper product that is analyzed using the above-described techniques.Notably, the paper product has a three-dimensional structure thatincludes a plurality of domes separated by land areas. As describedabove, such a paper product can be made using a structuring fabric. If,however, the specific structuring fabric configuration that was used tomake such a product was not known, a process according to the inventioncan be used to identify the structuring fabric configuration. As shownin FIG. 11A, an outline 802A can be drawn on the image of the paperproduct using the analysis program in a land area of the paper product,which corresponds to the position of a knuckle in the structuring fabricused to make the paper product. Further, a coordinate system includingguidelines 812 and 814 can be drawn through the outline 802A, and thepositions that correspond to other knuckles. Note that the domes in thepaper product correspond to the pockets in the structuring fabric, andaccordingly, the coordinate system is drawn without passing through thedomes.

After the outline 802A is formed and the coordinate system withguidelines 812 and 814 are drawn, as shown in FIG. 11A, the outline 802Aand coordinate system may be matched to images of fabrics so as todetermine a configuration that produces the three-dimensional structureof the paper product. An example of such a match is shown in FIG. 11B,wherein the outline 802A of and coordinate system with guidelines 812and 814 are overlaid upon an image 800A of a fabric. Note that theoutline 802A matches the size and shape of a knuckle in the fabric, andthat the guidelines pass through the knuckles, but not the areas thatcorrespond to pockets in the fabric. This matching indicates that thefabric shown in image 800A could be used to produce a paper productsimilar to that shown in image 800.

Matching the outline and coordinate system from a paper product to aparticular fabric may be facilitated by creating a searchable databaseof known fabrics. Such a database would include thepreviously-determined contact surface characteristics of fabrics, suchthe knuckle sizes, locations, pocket sizes, etc. After determining thesizes and positions for the knuckles and pockets of the fabric from theoutline and coordinate system formed from the paper product, thedatabase could be searched for fabrics with similar sizes and positionsof knuckles and pockets.

To facilitate the process of matching an analyzed image of a paperproduct with a fabric, additional parameters may be used that aredeveloped in the analysis of the paper product. One such additionalparameter is the frequency that one set of guidelines crosses aguideline from the other set of guidelines. Note, a “set” of guidelinesrefers to parallel guidelines, e.g., the guideline 812 and all theguidelines parallel thereto to form a set. In FIG. 11A, the frequency ofthe set of guidelines that includes guideline 812 would be calculated,for example, having the analysis program determining the distancebetween two of the guidelines crossing guideline 810, as measured alongone guideline 810. For example, if the guidelines crossing guideline 810were spaced 0.130 cm apart as measured along the guideline 810, then thecrossing guidelines would have a frequency of 7.7 cm⁻¹ (1/0.130 cm). Asimilar frequency calculation could be done for the other set ofguidelines that cross guideline 812 by measuring the spacing between theguidelines of this set along one of the guidelines 812. Once determined,the frequency in the guideline spacing for a paper product could bematched to the previously determined frequency of guideline spacing forfabrics, which have been stored in a searchable database.

Another parameter that can be calculated to facilitate the process ofmatching the outlined knuckle and guidelines from a paper product to aparticular fabric is the angle to the guidelines of a set from areference line. For example, the scale line SC in FIG. 11A could be usedas a reference, and the angle a could be determined between the scaleline SC and one set of the guidelines. The angle from the scale line SCto the other set of guidelines could also be determined. Oncedetermined, the angles from the reference to the sets of guidelines fora paper product could be matched to the previously determined anglesfrom the reference to the sets of guidelines for fabrics, which havebeen stored in a searchable database.

While the above-described methods are described in terms of matching apaper product to a known fabric, it will be readily appreciated thatother embodiments include selecting a known fabric made on a desired,but not yet produced, three-dimensional paper structure. That is, anoutline knuckle or knuckles could be created in a blank image, and aknuckle and pocket pattern could be created by drawing guidelines in theblank image. The created image could then be matched with a known fabricin the manner described above.

In yet another embodiment, a fabric could be designed and manufacturedbased on the analysis of a paper product image or based on a createdimage representing a knuckle and pocket configuration. In this method,warp and weft yarns are chosen to correspond to the desired knuckle andpocket configuration, as determined by analysis of the paper productimage or created in a blank image. Techniques for producing fabrics withparticular weave patterns of warp and weft yarns are well known in theart. Thus, a fabric could be produced with the chosen warp and weft yarnconfiguration.

In other embodiments of my invention, the fabric characterizationtechniques described herein can be used to modify the configuration of afirst papermaking fabric in order to produce a new, second papermakingfabric having different characteristics. In these embodiments, at leastone knuckle or pocket characteristic of the first papermaking fabric isdetermined with the above-described techniques. The characteristic maybe, for example, one or more of the characteristics described in TABLE 1or TABLE 2 above. Further, the characteristic may be the pocket depth oreffective pocket volume, which are determined according to theabove-described techniques. Based on the determined characteristic(s), amodified fabric design is created wherein the characteristic(s) arechanged. For example, the pocket depth may be increased from the pocketdepth measured in the first papermaking fabric. Those skilled in the artwill appreciate the factors that determine the characteristics of apapermaking fabric, and as such, will appreciate how the design of thefirst papermaking fabric may be altered to produce the new papermakingfabric having the different characteristics. For example, an aspect ofthe fabric such as one or more of yarn diameters, yarn densities, yarnshapes, weave patterns, and the heat setting used to bond the yarnstogether, could be altered to produce the second papermaking fabric thathas the modified characteristic(s). One of many examples of papermakingfabric manufacturing techniques utilizing some of these factors can beseen in U.S. Pat. No. 6,350,336, the disclosure of which is incorporatedby reference in its entirety.

In addition to, or in conjunction with, the embodiments for modifyingthe configuration a papermaking fabric design, the characteristics ofpaper products made using the structuring fabrics can be used in thedevelopment of a papermaking fabric having particular characteristics.For example, the characteristics of a first papermaking fabric can bedetermined using the above-described techniques. The first papermakingfabric can also be used to make a papermaking product, for example,using the papermaking methods described above. The characteristics ofthe paper product can then be determined, and thereafter correlated withthe determined characteristics of the first papermaking fabric. Forexample, the densities and heights of the domes formed in the paperproduct can be measured by examining the domes with a microscope. Asdiscussed above, the domes are formed in the pockets of the papermakingfabric. It follows that the pocket density and pocket depth determinedin a papermaking fabric can be correlated to a dome density and domeheight found in a paper product that was made using the papermakingfabric. Such correlations can then be used to determine what paperproduct could be expected to be made with another papermaking fabrichaving comparable characteristics. Further, as described above, a newpapermaking fabric design could be developed, with adjustedcharacteristics in order to produce paper products with modifiedcharacteristics as desired.

Although this invention has been described in certain specific exemplaryembodiments, many additional modifications and variations would beapparent to those skilled in the art in light of this disclosure. It is,therefore, to be understood that this invention may be practicedotherwise than as specifically described. Thus, the exemplaryembodiments of the invention should be considered in all respects to beillustrative and not restrictive, and the scope of the invention to bedetermined by any claims supportable by this application and theequivalents thereof, rather than by the foregoing description.

I claim:
 1. A process of determining characteristics of a papermakingfabric, the process comprising: forming an image of a portion of asurface of the papermaking fabric, with knuckles and pocket areas of thepapermaking fabric being shown in the image; displaying the image on ascreen associated with a computer; and forming guidelines on the imageon the screen, with the guidelines passing through knuckles shown in theimage, and with the guidelines forming non-rectangular parallelogramshapes that surround the pocket areas between the knuckles shown in theimage; and a step of calculating at least one characteristic related tothe knuckles or pocket areas of the papermaking fabric, with theguidelines formed on the image being used in the calculation.
 2. Theprocess according to claim 1, wherein the image is formed from arepresentation of the papermaking fabric, with the representation beingformed by one of (i) pressing the surface of the papermaking fabricagainst pressure measurement film, (ii) taking a photograph of thesurface of the papermaking fabric, and (iii) pressing the surface of thepapermaking fabric against wax paper.
 3. The process according to claim1, wherein the guidelines are formed such that the guidelines passthrough center regions of the knuckles shown in the image.
 4. Theprocess according to claim 1, wherein the calculating step includesusing a scale at which the image is displayed on the screen to determinea distance between at least two of the guidelines.
 5. The processaccording to claim 1, wherein the at least one characteristic is atleast one of (i) a length of a knuckle, (ii) a width of a knuckle, (iii)a frequency of the guidelines, (iv) an intersecting angle of theguidelines, (v) a knuckle density, (vi) a knuckle contact area, and(viii) an area of a pocket.
 6. The process according to claim 1, whereinan outline is formed around at least one of the knuckles shown in theimage, and the outline is used in the calculation step.
 7. A process offorming a new papermaking fabric having properties that are differentthan corresponding properties of an original papermaking fabric, themethod comprising: (A) determining at least one characteristic relatedto knuckles or pockets on a surface of the original papermaking fabric,the determinating comprising steps of: (a) forming an image of a portionof a surface of the original papermaking fabric, with knuckles andpocket areas of the fabric being shown in the image; (b) displaying theimage on a screen associated with a computer; and (c) forming guidelineson the image on the screen, with the guidelines passing through knucklesshown in the image, and with the guidelines forming non-rectangularparallelogram shapes that surround the pocket areas between the knucklesshown in the image; and (d) a step of calculating a value of the leastone characteristic of the original papermaking fabric using theguidelines formed on the image; and (B) forming the new papermakingfabric such that a corresponding value of the at least characteristic inthe new papermaking fabric is different than a calculated value of theat least one characteristic in the original papermaking fabric.
 8. Theprocess according to claim 7, wherein the image is formed from arepresentation of the papermaking fabric, with the representation beingformed by one of (i) pressing the surface of the papermaking fabricagainst pressure measurement film, (ii) taking a photograph of thesurface of the papermaking fabric, and (iii) pressing the surface of thepapermaking fabric against wax paper.
 9. The process according to claim7, wherein the guidelines are formed such that the guidelines passthrough center regions of the knuckles shown in the image.
 10. Theprocess according to claim 7, wherein the calculating step includesusing a scale at which the image is displayed on the screen to determinea distance between at least two of the guidelines.
 11. The processaccording to claim 7, wherein the at least one characteristic is atleast one of (i) a length of a knuckle, (ii) a width of a knuckle, (iii)a frequency of the guidelines, (iv) an intersecting angle of theguidelines, (v) a knuckle density, (vi) a knuckle contact area, and(viii) an area of a pocket.
 12. The process according to claim 7,wherein an outline is formed around at least one of the knuckles shownin the image, and the outline is used in the calculation step.